1. Field of the Invention
The present invention relates generally to implantable medical devices, and more particularly, to portable power charging of implantable medical devices.
2. Related Art
Medical devices having one or more implantable components, generally referred to herein as implantable medical devices, provide a wide range of therapeutic benefits to recipients. Certain implantable medical devices, sometimes referred to as active implantable medical devices (AIMDs), include an implantable power supply that provides power to one or more implantable components. AIMDS include, but are not limited to, certain implantable hearing prostheses, neural stimulators, drug pumps and cardiac devices.
One type of hearing prosthesis that is widely used is the partially implantable cochlear implant. Traditionally, partially implantable cochlear implants consist of an external speech processor unit and an implanted receiver/stimulator unit. The external speech processor unit is worn on the body of the user, such as a behind-the-ear (BTE) device. BTE devices are generally configured to receive sound with a sound input element, such as a microphone, and to convert the received sound into an electrically coded data signal that is transcutaneously transferred to the implanted receiver/stimulator unit. The BTE device is also generally configured to transcutaneoulsy transfer power to the implanted receiver and stimulator unit. More particularly, the power and data are transcutaneously transferred via a magnetic induction link established in a reactive near-field between an external coil closely coupled to an implanted coil.
Traditionally, the operating power for the BTE device and implanted components is provided by batteries, such as Zn-Air batteries, housed in the device. The closely coupled coils include an external coil coupled to the BTE device which is configured to be placed in close proximity to the coil of the implanted component. However, due to improvements in power storage technology, it has become more common for implantable hearing prosthesis and other AIMDs to include an implantable power supply that is sufficient to allow for periods of operation without access to an external power source. Such implantable power storage has enabled certain devices, in particular hearing prostheses, to become totally or fully implantable.
In addition to an implantable power supply, totally implantable hearing prostheses also have one or more components that were traditionally external to the recipient, such as the sound processor, implantable in the recipient. Accordingly, totally implantable prostheses to operate independently (that is, without an external device) for periods of time. It would be appreciated that, as used herein, totally or fully implantable hearing prosthesis may include external devices such as microphones, remote controls, etc.
Various implantable power storage systems have been proposed. However, in all implantable systems it remains necessary to transfer power from an external power supply to recharge the implanted power storage system. Devices continue to use the closely coupled external/internal coils to transfer the power, although the headpiece coil is not continuously required for regular operation. Data transfer may occur using alternative wireless links, for example short range EM (electro-magnetic) links (e.g. 400 MHz) or MI (magnetic induction) links (e.g. 10.7 MHz).